Messageboxes suppressed by Juce?


firstly - thanks for the great platform. I've nearly transitioned totally, however, there are a couple of issues. I used the introjucer to create a audio plugin project which i then built my existing project out from.

I have my own api for creating messageboxes, but (at least on windows) when i spawn messageboxes, they do not appear - but still block the main gui. They appear if i press 'alt' for some reason.

What gives?



No.. there's nothing I can think of that would interfere with that. Maybe your boxes are just behind other windows, e.g. are the other windows always-on-top?

Nope.. On windows i use the native MessageBox() api btw. I can't seem to reproduce the problem with my old source (pure vst plugin).

If i spawn the messageboxes asynchronously, ie. in another thread, they work fine.


Another thing, the program crashes if i close the plugin while the messagebox is hidden - but i guess i have to lock it with a mutex, so the plugin doesn't get deleted meanwhile.


Edit: another thing, my plugin spawns another window, which can make messageboxes without problems.

If you're doing a plugin then don't run any modal loops! I'm so tired of repeating this, I can't bear to type out all the reasons for it yet again.. I should probably write some kind of sticky post or article about it.

In your particular case your problem is probably just that you're calling win32 GUI functions on a background thread that hasn't been initialised as a GUI thread. But do NOT fix it by messing about with win32 functions to force the threading to work - the only sensible fix would be to remove all modal loops from your plugin, and embed any message boxes inside your plugin's editor, not in floating windows.


Well im sorry if i ruined your evening :(

Sorry if my comment sounded a bit more grumpy than it was intended to! But please heed the advice - plugins with pop-up windows are a bad idea for everyone: annoying for users to dismiss when scanning or loading projects; a total nightmare for us host-writers to deal with; and it'll cause horrible subtle bugs for you if you run modal loops. Please don't do it!

Yes, i understand all the reasons. However this seems to not only be for audio plugins. Looking at the juce code in juce_gui_basics.cpp, it seems something about your WM_PAINT handler is incorrect.  There are certain cases (like for the reentrant code you commented yourself in case of messageboxes) where it is more appropiate to return DefWndProc() instead - this solves all problems i've had.

The WM_PAINT stuff has been pretty rock-solid for years now - which bit exactly are you talking about?